Signs That Your Horse May Lack Selenium

Signs of selenium deficiency in the adult horse often relate to performance and muscle function. Horses that lack selenium become stiff and prone to soreness associated with exercise, which can lead to reactive behavior and poor performance. Cardiac and respiratory function are affected as well. They may have a poor hair coat with a scant mane and tail. Hoof quality can also be affected, as can joint health. In addition, low selenium levels can suppress the immune system, leaving horses susceptible to infection. Mare and stallion fertility can be compromised in horses used for breeding. Finally, foals born with selenium deficiency can develop white muscle disease, which compromises their heart. These foals often fail to stand and nurse. 

The need for selenium supplementation is based on geography, as some areas produce forage that contains significant amounts of selenium, while other regions have selenium-deficient soil. Parts of the east and west coasts are selenium deficient, as well as the Great Lakes region. There are variations throughout the United States, so it is important to consult your veterinarian and know your area. 

Horses in deficient areas can be managed with a daily oral supplement. Most products contain 1-3mg of selenium per dose. Individual horses seem to vary in what they require. A simple blood test can accurately measure selenium levels. This provides an excellent tool for evaluating supplementation. It is important to be aware that selenium toxicity can be just as problematic as deficiency, so over-supplementation needs to be avoided as well.